How Harley-Davidson Works

The Harley Mystique and the Distinctive Sound

Where does the Harley mystique come from? Think about a Marlboro cigarette. It's simply a bit of tobacco wrapped in paper. There are hundreds of other brands of cigarette that are nearly identical, but the Marlboro brand has mystique. Part of it comes from image advertising, but the other part is cultural. The people who smoke Marlboro cigarettes tend to be a certain type of person. Because they advertise and reinforce the brand image, they in turn attract more of their kind to the brand -- and so on.

In the case of Harley-Davidsons, although some amount of advertising is done, far more of the brand image comes about in other ways:

  • The use of Harleys in the movie and television industry.
  • The huge Harley rallies that can attract over 100,000 bikers.
  • The people who ride Harleys, and the image they project in public.
These elements along with a few others create a resonating, grassroots type of promotion that is extremely rare, but fascinating when it happens. This begins to convey the Harley mystique. Now let's discuss something else that resonates -- the telltale Harley sound.

There is no denying that a Harley-Davidson motorcycle has a unique sound, especially if the mufflers have been removed. The sound is part of the mystique. The reason for the sound has to do with the way the engine is designed.

the 2002 Ultra Classic Electra Glide
Photo courtesyHarley-Davidson Motor Company
Favorably fitted and ready for the road, the 2002 Ultra Classic® Electra Glide® is equipped with the Twin Cam 88® Engine, air-adjustable rear touring suspension and triple-disc brakes.

If you have read the HowStuffWorks article How Car Engines Work, then you know how a basic four-stroke gasoline engine operates. A piston goes through the intake, compression, combustion and exhaust strokes every two revolutions of the crankshaft. When your lawn mower is idling, you can hear the pop-pop-pop-pop sound of the individual strokes. What you are actually hearing is the sound of the compressed gases in the cylinder escaping when the exhaust valve opens. Each pop is the sound of the exhaust valve opening one time, and it happens on every second revolution of the crankshaft.

In a two-cylinder, horizontally opposed engine, the pistons are timed so that one fires on one revolution of the crankshaft and the other fires on the next revolution -- so one of the two pistons fires on every revolution of the crankshaft. This seems logical and gives the engine a balanced feeling. To create this type of engine, the crankshaft has two separate pins for the connecting rods from the pistons. The pins are 180 degrees apart from one another.

A Harley engine has two pistons. The difference in the Harley engine is that the crankshaft has only one pin, and both piston rods connect to it. This design, combined with the V arrangement of the cylinders, means that the pistons cannot fire at even intervals. Instead of one piston firing every 360 degrees, a Harley engine goes like this:

  • A piston fires.
  • The next piston fires at 315 degrees.
  • There is a 405-degree gap.
  • A piston fires.
  • The next piston fires at 315 degrees.
  • There is a 405-degree gap.
And the cycle continues.

At idle, you can hear the pop-pop sound followed by a pause. So the sound of a Harley is pop-pop...pop-pop...pop-pop. That is the unique sound of a Harley-Davidson motorcycle.

The Name Game
William Davidson, Walter Davidson, Arthur Davidson and William Harley
Photo courtesy Harley-Davidson Motor Company Archives
From left to right: William Davidson, Walter Davidson, Arthur Davidson and William Harley.
The Harley-Davidson Motor Company got its name from founders William S. Harley and Arthur Davidson. In time, Davidson's brothers, William and Walter, joined the company.

According to the Harley-Davidson Archives, Harley's name comes first because "it was his drafting, designing and testing that made the first motorcycles ever produced by the young company a possibility." The men included the hyphen in the name so that it would be clear that the company had two founding fathers, not just one.